diff --git a/lib/internal/Magento/Framework/Mail/Message.php b/lib/internal/Magento/Framework/Mail/Message.php
index 71da6e673bf29..a9996c0a4f12a 100644
--- a/lib/internal/Magento/Framework/Mail/Message.php
+++ b/lib/internal/Magento/Framework/Mail/Message.php
@@ -23,7 +23,7 @@ class Message implements MailMessageInterface
      *
      * @var string
      */
-    private $messageType = self::TYPE_TEXT;
+    private $messageType = Mime::TYPE_TEXT;
 
     /**
      * Initialize dependencies.
@@ -58,8 +58,8 @@ public function setMessageType($type)
      */
     public function setBody($body)
     {
-        if (is_string($body) && $this->messageType === MailMessageInterface::TYPE_HTML) {
-            $body = self::createHtmlMimeFromString($body);
+        if (is_string($body)) {
+            $body = self::createMimeFromString($body, $this->messageType);
         }
         $this->zendMessage->setBody($body);
         return $this;
@@ -157,18 +157,19 @@ public function getRawMessage()
     }
 
     /**
-     * Create HTML mime message from the string.
+     * Create mime message from the string.
      *
-     * @param string $htmlBody
+     * @param string $body
+     * @param string $messageType
      * @return \Zend\Mime\Message
      */
-    private function createHtmlMimeFromString($htmlBody)
+    private function createMimeFromString($body, $messageType)
     {
-        $htmlPart = new Part($htmlBody);
-        $htmlPart->setCharset($this->zendMessage->getEncoding());
-        $htmlPart->setType(Mime::TYPE_HTML);
+        $part = new Part($body);
+        $part->setCharset($this->zendMessage->getEncoding());
+        $part->setType($messageType);
         $mimeMessage = new \Zend\Mime\Message();
-        $mimeMessage->addPart($htmlPart);
+        $mimeMessage->addPart($part);
         return $mimeMessage;
     }
 
@@ -177,7 +178,7 @@ private function createHtmlMimeFromString($htmlBody)
      */
     public function setBodyHtml($html)
     {
-        $this->setMessageType(self::TYPE_HTML);
+        $this->setMessageType(Mime::TYPE_HTML);
         return $this->setBody($html);
     }
 
@@ -186,7 +187,7 @@ public function setBodyHtml($html)
      */
     public function setBodyText($text)
     {
-        $this->setMessageType(self::TYPE_TEXT);
+        $this->setMessageType(Mime::TYPE_TEXT);
         return $this->setBody($text);
     }
 }
diff --git a/lib/internal/Magento/Framework/Mail/Test/Unit/MessageTest.php b/lib/internal/Magento/Framework/Mail/Test/Unit/MessageTest.php
index 0c33e25e0d9d0..bea2a9ea91d38 100644
--- a/lib/internal/Magento/Framework/Mail/Test/Unit/MessageTest.php
+++ b/lib/internal/Magento/Framework/Mail/Test/Unit/MessageTest.php
@@ -5,44 +5,40 @@
  */
 namespace Magento\Framework\Mail\Test\Unit;
 
+/**
+ * test Magento\Framework\Mail\Message
+ */
 class MessageTest extends \PHPUnit\Framework\TestCase
 {
     /**
-     * @var \PHPUnit_Framework_MockObject_MockObject|\Magento\Framework\Mail\Message
+     * @var \Magento\Framework\Mail\Message
      */
-    protected $_messageMock;
+    protected $message;
 
     protected function setUp()
     {
-        $this->_messageMock = $this->createPartialMock(
-            \Magento\Framework\Mail\Message::class,
-            ['setBody', 'setMessageType']
-        );
+        $this->message = new \Magento\Framework\Mail\Message();
     }
 
     public function testSetBodyHtml()
     {
-        $this->_messageMock->expects($this->once())
-            ->method('setMessageType')
-            ->with('text/html');
+        $this->message->setBodyHtml('body');
 
-        $this->_messageMock->expects($this->once())
-            ->method('setBody')
-            ->with('body');
-
-        $this->_messageMock->setBodyHtml('body');
+        $part = $this->message->getBody()->getParts()[0];
+        $this->assertEquals('text/html', $part->getType());
+        $this->assertEquals('8bit', $part->getEncoding());
+        $this->assertEquals('utf-8', $part->getCharset());
+        $this->assertEquals('body', $part->getContent());
     }
 
     public function testSetBodyText()
     {
-        $this->_messageMock->expects($this->once())
-            ->method('setMessageType')
-            ->with('text/plain');
-
-        $this->_messageMock->expects($this->once())
-            ->method('setBody')
-            ->with('body');
+        $this->message->setBodyText('body');
 
-        $this->_messageMock->setBodyText('body');
+        $part = $this->message->getBody()->getParts()[0];
+        $this->assertEquals('text/plain', $part->getType());
+        $this->assertEquals('8bit', $part->getEncoding());
+        $this->assertEquals('utf-8', $part->getCharset());
+        $this->assertEquals('body', $part->getContent());
     }
 }